JPH04133415U - Chiyoke coil for high frequency - Google Patents

Abstract

(57) [Summary] [Purpose] Create air gaps in both outer legs of a Japanese-shaped magnetic core or an EE-type magnetic core, and wind the same number of windings in normal mode on both outer legs. To provide a high frequency choke coil which is effective in suppressing normal mode noise and common mode noise, and whose inductance value does not decrease up to the MHz band even when DC current is superimposed using two magnetic cores. [Configuration] Japanese-shaped magnetic core 1 or EE-type magnetic core 2
According to the present invention, air gaps 4 are provided in both outer legs 3 of a magnetic core (magnetic core having a plurality of magnetic legs in parallel), and windings 7 are applied so that the winding directions as seen from the input end or the output end are the same direction. It is used as a choke coil for high frequency.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This invention is used for the purpose of removing high-frequency electromagnetic noise in electronic equipment. This relates to a high frequency choke coil.

0002

[Conventional technology]

The propagation mode of high-frequency noise flowing into the power supply line of electronic equipment has at least one pair of propagation modes. The normal mode component is a reciprocating line between the power supply lines, and this normal mode component is Based on the basics, common models that use a round-trip line between the power line and the ground or between the chassis mainly due to distributed capacitance, etc. The conventional method for removing electromagnetic noise is as shown in (a) in Fig. 7. And as shown in FIG. 7(c), the normal mode choke coil 11 and the common Either the mode choke coil 12 is used in combination, or the mode choke coil 12 is used together, or the mode choke coil 12 is used together with the 1 of the magnetic circuit around which the winding of the magnetic core 14 constituting the mode choke coil is wound. By providing a void 13 in the part and actively creating leakage inductance, the - They were constructed and used to provide multi-mode inductance.

0003 When using normal mode choke coil and common mode choke coil together As shown in Fig. 7(a) and Fig. 7(c), three independent choke coils are used. The mounting area is large due to the use of magnetic cores (hereinafter referred to as cores) and Disadvantages include the need for three coils and higher costs due to material and processing costs. there were. In addition, as shown in Figure 7(b), the leakage-in of the common mode choke is A chip that actively increases inductance and produces normal mode inductance. If the normal mode inductance of the choke coil is increased too much, the inductance of the coil will decrease. Inductance L1 and inductance L2 create independently interlinked magnetic fields. As the flux φ2 increases, when line current is superimposed, the core becomes saturated and the inductance decreases. The disadvantage was that it decreased.

0004

[Problems to be solved by the invention] In order to eliminate the above-mentioned drawbacks of the conventional technology, the present invention aims to eliminate both normal mode and common mode noise in electronic equipment using only one magnetic core and normal mode winding. The purpose of the present invention is to provide a small and inexpensive high-frequency choke coil capable of direct current superposition and having a normal mode inductance value L _N equal to or higher than a common mode inductance L _C.

[0005]

[Means to solve the problem]

A space is provided in each of the outer legs of the Japanese-shaped magnetic core or the EE-shaped magnetic core. When current flows back and forth through the windings with the same number of turns wound on each outer leg, The magnetic flux generated in the center leg is caused by the magnetic fields generated by the windings wound on both outer legs striking each other. This is a high frequency choke coil with windings to eliminate the noise.

[0006] That is, the present invention has 1. A node flows between the windings in a magnetic core with multiple magnetic legs in parallel. High-frequency choke coils are wound in such a way that the multi-mode signals add up to each other. and a gap is provided between at least two magnetic legs of one magnetic core, and the gap is provided. Make sure that the winding directions are the same as seen from the input end and output end of each magnetic leg. Functions of common mode choke coil and normal mode choke coil This is a high frequency choke coil characterized by having the following characteristics. 2. Japanese-shaped magnetic coin Provide air gaps in both outer legs of the A or EE type magnetic core, and The wires are wound so that the winding directions as seen from the input end and output end are the same. This is a high frequency choke coil characterized by the following.

[0007]

[Effect]

A space is provided in each of the outer legs of the Japanese-shaped magnetic core or the EE-shaped magnetic core. When the number of windings wound on each outer leg is the same, the number of windings wound on both outer legs is equal. When a return current flows, the magnetic flux generated in both outer legs cancels each other out in the center leg. Since windings are applied to both outer legs of the sea urchin, for example, a large DC current can be applied to two parallel wires. Even when folded, the saturation of the magnetic core is determined by the air gap length provided on both outer legs, and the common In mode operation, the magnetic flux created by both outer legs acts to bias the central magnetic leg. , operates to increase the value of common mode inductance, so one magnetic Even when a large DC or AC current is superimposed on the winding wound around the outer leg of the core, the normal High frequency choke coil that operates effectively against common mode noise and common mode noise. files can be configured.

[0008]

【Example】

FIG. 1 is an external perspective view showing the configuration of a choke coil according to the present invention. FIG. 1(a) is an example of a magnetic core used in a high-frequency choke coil of the present invention, in which air gaps 4 are provided on both outer legs 3 of a sun-shaped magnetic core 1, and FIG. 1(b) is This is an embodiment of a magnetic core used in a high-frequency choke coil of the present invention, in which air gaps 4 are provided in both outer legs 3 of an EE type magnetic core. FIG. 1(c) shows a magnetic core in which air gaps 4 are provided on both outer legs of the EE type magnetic core 2 shown in FIG. 1(b), so that the winding directions as seen from the input end and the output end are the same as each other. This is an example of the high frequency choke coil of the present invention in which the winding 7 is arranged in the normal mode. In FIG. 1(c), a line current or, for example, a normal mode noise current I _N flows into the coil L ₁ from terminal A and flows out from terminal B. In FIG. Further, in the coil L ₂ , the air flows into the terminal D and flows out to the terminal C. The magnetic flux φ1 generated by the line current or normal mode noise current is generated in both outer legs 3 of the magnetic core in a direction in which the magnetic fluxes generated by the coils _L1 and _L2 are superimposed, that is, in a direction in which they are added, and the normal mode inductance L _However , air gaps 4 are provided in both outer legs 3 to reduce the effective magnetic permeability, and adjustments are made so that the magnetic core does not become saturated, so changes in the current superimposed on the windings occur. There is no decrease in inductance due to Further, in the central leg 8, the magnetic fluxes Φ1 generated by the coil L ₁ and the coil L ₂ are in opposite directions, so the normal mode inductance L _N is approximately determined by the length of the gap provided in the outer leg.

In FIG. 1C, a common mode noise current I _C (indicated by a broken line) flows into the L ₁ coil from terminal A and flows out to terminal B. In addition, in the L ₂ coil, it flows into terminal C and flows out to terminal D. Therefore, the magnetic flux φ ₂ generated by the common mode noise current I _C is in opposite directions on both outer legs of the magnetic core, that is, in directions that cancel each other out, and in the same direction on the center leg 8, that is, in a direction that adds up. The common mode inductance L _C is almost determined by the passing magnetic flux. Therefore, if the central leg 8 is saturated, the common mode inductance L _C decreases. However, since the common mode noise current is usually a weak current of several hundred μA to several tens of mA, it does not saturate the center leg and does not reduce the common mode inductance L _C , so there is no problem in practical use.

FIG. 2 shows a method for measuring normal mode inductance L _N and common mode inductance L _C. Figures 2(a) and 2(b) are circuit diagrams and configuration diagrams when measuring the normal mode inductance _LN , and when the wires are connected in a direction that adds the magnetic fluxes generated in the coils L ₁ and L ₂ . is the inductance of Figures 2(c) and 2(d) are circuit diagrams and configuration diagrams when measuring the common mode inductance L _C , and are shown when the wires are connected in a direction that cancels out the magnetic flux generated in the coils L ₁ and L ₂ . It is inductance. Next, an example in which a high-frequency choke coil of the present invention was actually manufactured and measured will be explained. The magnetic core has a width of 28 mm between both outer legs, a thickness of 10 mm, an outer leg width of 6 mm, and a center leg of 7 mm. Two EE type magnetic cores (Ni-Zn ferrite cores) having the dimensions and shape shown in Fig. 1(b) are combined (EE type), a gap of 1.5 mm is provided on each outer leg, and the number of turns is 10. A normal mode choke coil was formed by winding the windings so that the winding directions viewed from the input end or the output end were the same. Figure 3 shows the frequency characteristics of the inductance at that time, and Figure 4 shows the inductance characteristics when a DC current is superimposed on the inductor. The normal mode inductance L _N and the common mode inductance L _C shown in FIG. 3, in which direct current is not superimposed, both had inductance values of about 17 μH, and constant characteristics were obtained up to about 40 MHz in the frequency band. Further, even when the DC current shown in FIG. 4 is superimposed, the normal mode inductance L _N remains constant up to 12 A and is not saturated. The inductance value of the common mode inductance L _C starts to decrease when it is 2 A or more, but as mentioned earlier, the common mode noise current is less than several tens of mA, so in practical terms, the common mode inductance L _C does not decrease. FIG. 4 shows the inductance L _Na of a conventional normal mode inductor in which leakage inductance is actively increased in a conventional common mode choke coil. In the current superposition characteristic when (L _N a = L _C = 17 μH), a decrease in inductance L _N is observed below 1 A.

[0011] Next, the high frequency choke coil of the embodiment of the present invention having the characteristics shown in Figs. 3 and 4 was An example of the electromagnetic noise removal effect when implemented in a slave device is shown below. German standard as shown in Figure 5 A microwave oven was used as the test device according to the noise interference power measurement method according to the VDE standard. It was measured. As shown in Figure 6, the choke coil is connected to the magnetron input in Figure 6 (A). When installed in the power section and the power input section in Figure 6 (B), when no coil is inserted The noise that was generated at 66 dBPW at 34.4 MHz in the condition (A) is is 47.7 dBPW with only the conventional common mode choke, and 47.7 dBPW with only the conventional common mode choke. The choke coil according to the present invention had a power output of 39 dBPW. It was 35dBPW. In addition, in (B), the conventional common mode choke 42dBPW with only a conventional choke, and 62dBPW with only a conventional normal mode choke. In contrast, the choke coil according to the present invention had a power output of 38 dBPW.

0012

[Effect of the idea]

A gap is provided in both outer legs of the Japanese-shaped magnetic core or the EE-type magnetic core according to the present invention. , a normal mode choke coil with normal mode windings on both outer legs. By providing the function of a mode choke coil, a small and inexpensive electromagnetic noise We can provide high-frequency choke coils with excellent noise prevention function.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of a high-frequency choke coil according to the present invention; FIG. 1(a) is a perspective view showing an example of a sun-shaped magnetic core, and FIG. 1(b) is a perspective view showing an example of an EE-type magnetic core. FIG. 1(c) is a perspective view showing an embodiment of the high frequency choke coil according to the present invention.

[Fig. 2] A circuit diagram showing the wiring for normal mode and common mode inductance measurement.
(b) is the measurement circuit diagram in normal mode, (c) in Figure 2
FIG. 2(d) is a circuit diagram for measuring noise characteristics under common mode conditions.

FIG. 3 is an inductance frequency characteristic diagram when no direct current is superimposed on the winding of the high-frequency choke coil according to the present invention.

FIG. 4 is an inductance current superposition characteristic diagram when a direct current is superimposed on the winding of the high frequency choke coil according to the present invention.

FIG. 5 is a layout diagram showing a method for measuring noise interference power.

FIG. 6 is a circuit diagram schematically showing the mounting position when the choke coil according to the present invention was mounted in a microwave oven and the noise prevention effect was investigated.

[Figure 7] An example of a conventional noise filter that simultaneously prevents normal mode and common mode noise.
7 is a circuit diagram showing an example in which a common mode choke coil and a normal mode choke coil are connected in series, and _FIG . Fig. 7(c) is a characteristic diagram showing the characteristics when a direct current of the inductor for both normal mode and common mode is superimposed on the winding.

[Explanation of symbols]

1 Japanese-shaped magnetic core 2 EE type magnetic core 3 Lateral leg 4 void 6 Magnetic core center leg 7 Winding wire 8 Central leg 11 Normal mode choke coil 12 Common mode choke coil 13 void 14 Magnetic core

──────────────────────────────────────────────── ─── Continued from front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H01F 41/02 D 2117-5E

Claims (2)

[Scope of utility model registration request] Claim 1: A high-frequency choke coil formed by winding a magnetic core having a plurality of magnetic legs in parallel so that normal mode signals flowing between the windings are added to each other, wherein at least two magnetic legs of one magnetic core An air gap is provided, and wires are wound around the magnetic legs provided with the air gap so that the winding directions seen from the input end and the output end are the same as each other, and have the functions of a common mode choke coil and a normal mode choke coil. High-frequency choke coil featuring: 2. A gap is provided in each of the outer legs of the Japanese-shaped magnetic core or the EE-type magnetic core, and the winding direction of the outer legs is wound in the same direction as viewed from the input end and the output end, respectively. A high frequency choke coil characterized by a wire.